Initially designed to treat sleep disorders like narcolepsy, idiopathic hypersomnia, sleep apnea and shift work sleep disorder, Modafinil's "off-label" use as a cognitive stimulant, and widespread use by soldiers and students alike, make it one of the most popular nootropic (performance enhancing) drugs purchased from internet pharmacies. The neurochemical substrates of modafinil are unresolved, but it works by modulating certain monoamine neurotransmitters. Modafinil assists in meeting the requirement to grasp the next window of opportunity, stay alert, be attentive, and memorize more and more sensory data.